Rolling mill

ABSTRACT

A rolling mill stand includes a pair of spaced apart housings each defining a window having a pair of blocks projecting therein from opposite sides of the housing. A pair of horizontal work rolls are arranged one above the other and are supported in bearing chock assemblies located in the housing windows. The rolls are displaceable in the direction of their length. Roll bending forces may be applied at the ends of the rolls by hydraulic rams acting vertically between the blocks and the bearing chock assemblies. The outer end of each ram, where it engages the bearing chock assembly, includes a body which is rotatably mounted on the ram and permits relative movement between the ram and the bearing chock assembly when the rolls are displaced in the direction of their length.

BACKGROUND OF THE INVENTION

This invention relates to rolling mills having provision for applyingroll bending forces to the work rolls of the mill.

It is known to apply bending forces to the bearing chock assembliesmounted at opposite ends of the work rolls of a mill by positioningfluid operated rams in parts of the mill housing which project into themill window. These parts may be integral with the housing or may takethe form of blocks which are secured to opposite walls of the housing.In these blocks, rams are located such that the piston of one ramprojects from the top of the block and is engageable with the undersideof a part of the bearing chock assembly on one roll and another pistonprojects from the underside of the block and bears against an upwardlydisposed surface on the bearing chock assembly of the other roll. Whenthe bearing chock assemblies are only free to move vertically towardsand away from each other, there are no particular problems because theline of action of the rams is also vertical. In certain applications,however, it is desirable that the work rolls should be displaceableaxially and, thus, in addition to moving vertically, the bearing chockassemblies at the ends of the work rolls must also be free to moveaxially of the roll thereby moving in the direction at right angles tothe line of action of the fluid operated rams. This can result in damagebeing caused to the rams, particularly if an attempt is made to move therolls axially while the rams are energised to apply bending forces tothe rolls by way of the bearing chock assemblies.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome this difficulty.

The present invention resides in a rolling mill stand comprising ahousing structure; a pair of horizontal work rolls arranged one abovethe other and each supported at their ends in bearing chock assemblieswhich are located in the housing structure; means for displacing therolls in the direction of their length; roll bearing means for applyingroll bending forces at the ends of the rolls, said roll bending meanscomprising hydraulic rams acting vertically between the housingstructure and the bearing chock assemblies and wherein the outer end ofeach ram where it engages the bearing chock assembly is constituted by arotatable body which permits relative movement between the ram and thebearing chock assembly in the direction of movement of the bearing chockassembly when the rolls are displaced in the direction of their length.

By making the outer end of each ram in the form of a rotatable body, theforce is applied between the ram and the chock, even when there isrelative axial movement between the chock and the block in which the ramis located. The axial movement causes the rotatable body to rotate inthe housing in which it is located, the housing forming part of thepiston of the ram.

The rotatably body is conveniently a sphere in the form of a steel ballwhich is partly located in a recess in the end of the piston and theball projects through an aperture in a retaining cover fitted to the endof the piston.

In an alternative arrangement, a roller is pivotally mounted in theouter end of the ram with part of the periphery of the roller projectingbeyond the housing which retains the roller in the piston. The axis ofrotation of the roller is such as to readily enable the roller to rotateabout this axis when there is relative movement between the roller andthe chock against which it bears in the axial direction of the rollsupported by the chock.

It is usual that in each block there are a pair of bending ram groupsarranged symmetrically on opposite sides of the centre line of thebearing between the end of the work roll and the chock against which thebending groups abut. Each group may consist of a single ram or a pair oframs situated in side-by-side relation. When the roll, and hence, itsbearing chock assembly is fixed relative to the rams, there are noparticular difficulties so long as the ram groups are symmetrical withthe centre line of the bearing between the roll and the chock assembly.However, when the roll is displaceable axially with respect to the blockin which the bearing ram groups are positioned, out of balance forceswill exist when axial displacement occurs. In this type of rolling mill,whether or not there is a rotatable body at the end of each ram, thepressures exerted by the groups of bending rams in each block arecontrolled to maintain the following relationship:

    P.sub.1 /P.sub.2 =(L/S-1

where P₁ and P₂ are the pressures generated by the respective bendingram groups, L is the distance between the centres of these two groups,and S is the offset of one bearing group from the axial centre of thework roll bearing.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood, it will nowbe described, by way of example only, with reference to the accompanyingdrawings in which:

FIG. 1 is an end view of part of a rolling mill showing the position ofthe bending rams;

FIG. 2 is a section through a bending ram; and

FIG. 3 is a sketch indicating the relative positions of the bending ramgroups and the forces produced by them.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a mill housing 1 defines a window 3 containing apair of chocks 5, 7 mounted at the corresponding end of a pair of upperand lower work rolls, respectively. The chock 5 has a pair of outwardlyextending wings 9 which are located above blocks 11 located on oppositewalls of the housing and the chock 7 has a pair of wings 13 whichproject below the blocks. In each of the blocks there a number ofbending ram groups which act against the wings 9, 13, respectively, inorder to apply bending forces to the work rolls.

As shown in FIG. 2, one of the bending rams comprises a cylinder 15formed in the block 11 with a double-acting piston 17 displaceablewithin the cylinder. The outer end of this piston is recessed to containa rotatable body in the form of a metal sphere 19 which is held inposition in the recess by an apertured cover 21 through which a part ofthe periphery of the sphere projects. Lubricant is supplied to thesurface of the sphere 19 by way of an axial feed tube 23 formed in thepiston 17.

The sphere 19 bears against a wear plate 25 let into the wing 9 of thetop chock 5.

FIG. 3 shows a work roll having a bearing chock assembly 5 at one end.Against the underside of this chock there are a number of bending ramswhich are engageable with the underside of the chock in order to applybending forces to the work roll. The bending rams are arranged in twogroups, referred to as group 31 and group 33, respectively. These groupsare located symmetrically about the centre line of the work roll bearingwith the centre line of each group being separated by a distance S fromthe centre line of the bearing and with the centre lines of the bearingsseparated by a distance L. In the position shown, the bending forces P₁,P₂ generated by the bending rams groups when they are energised would bearranged to be equal in the symmetrical position shown in the figure.When, however, the roll is shifted axially, the bending ram groups areno longer symmetrical with respect to the centre line of the work rollbearing and, in order to prevent misaligned forces being applied to thebearing chock, the pressure generated by the rams is controlled tomaintain the following relationship:

    P.sub.1 /P.sub.2 =(L/S)-1

L

where P₁ and P₂ are the pressures generated by the respective bendingram groups, L is the distance between the centres of these two groups,and S is the offset of one bearing group from the centre line of thework roll bearing.

Signals can be obtained from a transducer mounted on the actuator fordisplacing the work rolls in order to provide a signal representative ofthe offset S and the pressure of the fluids supplied to the bending ramgroups is adjusted accordingly.

What is claimed is:
 1. A rolling mill stand comprising:a housingstructure including a pair of spaced apart housings each defining awindow having a pair of blocks projecting therein from opposite sides ofthe housing; a pair of horizontal work rolls arranged one above theother and each supported at its ends in bearing chock assemblies whichare located in the housing windows; means for displacing the rolls inthe direction of their length; means for applying roll bending forces atthe ends of the rolls, said means comprising hydraulic rams actingvertically between the blocks and the bearing chock assemblies; and abody rotatably mounted on an outer end of each ram, where it engages abearing chock assembly, which permits relative movement between the ramand the bearing chock assembly when the rolls are displaced in thedirection of their length.
 2. A rolling mill stand as claimed in claim1, in which each ram comprises a cylinder defined by one of said blocks,a piston displaceable in the cylinder and an outer end of said piston,where it engages a bearing chock assembly, includes a sphere which isrotatably mounted on the piston.
 3. A rolling mill stand as claimed inclaim 11, in which the sphere is partly located in a recess in the endof the piston and projects through an aperture in a retaining coverfitted to the end of the piston.
 4. A rolling mill stand as claimed inclaim 1, in which each ram comprises a cylinder defined by one of saidblocks, a piston displaceable in the cylinder and an outer end of saidpiston, where it engages a bearing chock assembly, includes a rollerwhich is rotatably mounted on the piston.
 5. A rolling mill stand asclaimed in claim 1, in which in each window there are a plurality ofhydraulic rams acting vertically between each block and each bearingchock assembly, said plurality of rams being arranged in two groups withthe groups arranged one behind the other in the direction of axialmovement of the rolls.
 6. A rolling mill stand as claimed in claim 13,in which the pressures exerted by the groups of bending rams in eachblock are controlled to maintain the following relationships:

    P.sub.1 /P.sub.2 =(L/S-1

where P₁ and P₂ are the pressures generated by the respective bendingram groups, L is the distance between the centres of the two groups, andS is the offset of one group of bending rams from the axial centre ofthe work roll bearing.